


After Me, the Deluge

by Vulgarweed



Category: Sherlock (TV)
Genre: Bad Science, Dark Past, Don't Overthink This, Just Roll With It, Multi, Pretty Sure This Will Not Be S4 Compliant, Threesome - F/M/M
Language: English
Status: Completed
Published: 2017-01-01
Updated: 2017-01-01
Packaged: 2018-09-14 00:17:38
Rating: Explicit
Warnings: No Archive Warnings Apply
Chapters: 1
Words: 3,034
Publisher: archiveofourown.org
Story URL: https://archiveofourown.org/works/9148420
Author URL: https://archiveofourown.org/users/Vulgarweed/pseuds/Vulgarweed
Summary: Dark secrets of Mary’s past are coming to light, with unimaginable consequences for her, and for John, and for Sherlock.The trigger word is “architeuthis.”***(That’s really all the summary you’re getting right now. It’s cracky and smutty, and it’s true that No Archive Warnings Apply, and that’s all I’ll say. If you want to find out what Mary’s dark secret is, you have to read it. Mind the rating and pairing.)





	

Oh.

OH.

Had Sherlock allowed himself to be distracted by his own reflection in the laptop screen, he’d have seen his eyes in perfect roundness showing whites all the way around his irises, his mouth an immense oval gape.

But he was blinded by the white light in his mind, that perfect apotheosis of synthesizing information.

The jump drive did not provide the complete picture, of course. He’d half expected it to be blank, or filled with meaningless random data. It was neither. It was also just as well John had elected to ignore it, for he would not have gotten much from the first level of files that his imagination couldn’t have already filled in.

John never said in quite so many words that he was leaving it lying around untended for passive-aggressive purposes, of course, perhaps not even fully acknowledging to himself that his best friend was a habitual pickpocket who couldn’t resist violating privacy anymore than a dog can help snacking on the kitty litter.

But then, the first layer of information was a disappointingly mundane collection of childhood photos, disguises, aliases, and an admittedly rather impressive dossier of contacts, itineraries, and crime scenes.

The crux of the matter was the second layer, encoded deeply in ciphers-within-ciphers that only the baby brother of the British Government would have a hope of decoding (at least without getting the Russians involved).

And Sherlock was in _awe._

Words and images overlapped and separated out, fitting into each other for moments and coming unwoven again to reweave and recombine, as Sherlock’s eyes flew over the encrypted text and his fingers flew over the keys.

_Baskerville...human subject ethical protocols...advanced hydrotherapeutics derivations...pressurization training...genetic modification, grafting...code name hydra...biological enhancement, marine division…_

He slammed the laptop shut and sat there breathing hard, aflame with the glory and terror of his own epiphany.

 

***

“So…” Mary said, her full lips a tense-pressed line and her big eyes wary and sad. As far as Sherlock could tell, that was sincere. John was still a closed book but for his trembling hand and flickering tongue. “How are you healing?”

“Very well, thank you,” Sherlock said, rising to his feet smoothly and effortlessly. “One might almost think I had some sort of...cultivated mutation...to facilitate it. I don’t, of course. To my knowledge at least, who knows what may have happened when I was unconscious.”

Mary cocked her eyebrow and tilted her head, trying with all her might to give the effect of being kind to the ravings of a man probably still under the effect of painkillers. But there was a flicker. OH so brief, so barely-there. Mary really was remarkably good at her job. _Almost_ good enough to fool Sherlock Holmes.

“Tea?” said Sherlock giddily, lurching towards the kitchen.

“Oh, I should--” John said, trying to intercept him.

“Oh no,” Sherlock said. “Normal activity level is good for me, physical therapist’s orders.”

But as he passed Mary, he winced and stumbled for a moment. She turned instinctively to catch him, and he leaned down over her, steadying himself with a hand on her back.

On a very specific place on the left side just over her coccyx, and he felt her shudder and stiffen, her breathing going sharp and then still. For a split second she could still believe it was coincidence. Until he pressed his fingers at that certain spot, and whispered in her ear a single long word, elegant and ominous, hissing with its _th_ and _s_ sounds.

Mary pressed her eyes shut, and then she screamed.

John was on his feet in a flash - and Sherlock was off his, knocked to the ground as Mary’s blouse and jeans and jacket split at the seams, and great rippling cables of moist blue-grey flesh and muscle erupted from the sides of her body. With mighty force they unfurled to their full length, knocking over furniture and seeming almost to sniff at Sherlock and John as if they were sensory organs. Which, very likely, they were.

Mary stood shivering but still undaunted in the ruins of her clothes as her eight thick tentacles rippled obscenely and gracefully, as thick as bridge cables. 

“How...did...you...know?” she asked Sherlock flatly, chin held high. “I know you read my file. I knew John might not, but you would. But I didn’t think even you would know to look for the second layer.”

Sherlock laughed, sitting on the floor - it was a warm, full-bodied laugh, and his chest didn’t ache at all. Oh, he _was_ feeling the healing powers of a good deduction. “It was your wetwork dossier that tipped me off that there was much more to find out, Mary. The scenes of your crimes. I know what is and is not possible to do - for an assassin with only two hands.”

John’s expression had gone so far beyond gobsmacked that it was no longer in the universe with any gobs left to smack. Like a killer rabbit, he bared his teeth and twitched his nose, breathing in the vaguely oceanic scent of Mary’s long-hidden enhancements.

“How...how…” he finally managed to stammer. “I’m a _doctor._ I’ve seen you _naked._ A _lot._ We’ve had sex. A _lot._ ”

“Concealable gene-splice biotech,” Mary said wearily. “Activated by a trigger word. Which no one was supposed to know.”

“And yet, you deliberately sent your top-secret jump drive into the hands of one of the very few people who could deduce your secret, and yet have not immediate motive to exploit you for it. That is suggestive of someone who _wants_ their secret out,” said Sherlock, still sitting half-splayed on the rug, eyes gleaming.

“I didn’t give it to _you,”_ Mary said.

“Please,” said Sherlock.

“All right, fine. I didn’t really believe John would be able to keep it away from you.”

“He didn’t try very hard,” said Sherlock, evenly, trying to stay still as two of the tentacle tips began waving towards him, only slightly menacing.

“And…” John swallowed. “The . . . baby?”

“Is fine,” Mary said quickly. “Emergence doesn’t affect her.”

“Good to know, but…”

“Are you asking if she’s going to have tentacles too, John? She’s still our child even if she’s a squid!”

“That...wasn’t what I meant,” John said. “Of course she’s our child, but…”

“The answer is I don’t know,” Mary said. “This is all very new and very secret research. For enhancement of...assets. The chromosomal changes, if any, are unknown.”

“You’re one of the first,” Sherlock said, audibly impressed. “This is what even _we_ didn’t get to see at Baskerville. There’s so much more to it than hallucinogenic gas and glowing rabbits.”

“What?” Mary said. “Glowing rabbits?”

“Not relevant,” Sherlock said, waving his hand dismissively. The tip of one of Mary’s tentacles seemed to follow the movements of his hand like a snake charmer’s pet, and as he watched, fascinated, it split itself open like a flower, waving a mass of smaller and more delicate fleshly cilia.

Another of Mary’s tentacles was investigating John, and it seemed to like what it was finding, for it nuzzled him up and down, chin to chest, its tip opening in a similar way to explore him with nimble, boneless fingers. “Oh wait...wait, what do you think you’re doing?” he finally blurted indignantly as the little pulsing graspers slid down his belly and began to insinuate themselves between his buttons - then dipping lower still and taking liberties.

“Oh, let them have their fun, John, they’ve been penned up long enough,” said Sherlock. He started to say more but his deep voice turned decidedly squeaky as one of the little fingerlings swirled around his ear and lapped at him, surprisingly moist and feeling for all the world like a tongue.

“Oh God,” John moaned as the tentacle tip squirmed between his thighs and rippled. “Oh God, Mary, what are you doing?”

“I...could stop them, I _think,_ ” she said, even as two more of them reached out for John and made as if to curl around his waist and shoulders. “They’ve never acted like this before. Of course, I’ve never had them out in the presence of a sexual partner before, so….”

She was interrupted by a breathy little gasp, as another of her treacherous tips had wormed its way into the collar of Sherlock’s shirt and down his chest, and that was more than his already overtaxed buttons could take. Sherlock groaned as the soft and smooth but powerful appendage caressed his bared torso, seeming to take special care with the healing small scar.

“Him too?” John squeaked.

“I don’t know!” Mary yelled. “I haven’t! We haven’t! I promise!”

“True, we haven’t,” Sherlock said, as the tentacle grasped him gently but firmly and started to slowly drag him across the floor, in the general direction of Mary. “But it seems like at least part of you is fond of the idea.”

“I have to sit down,” John said, but he never quite made it to a chair, as the powerful appendages picked him up at arse and knees and delivered him to Mary in one smooth, swaying motion. Sherlock was similarly caught, and he and John could barely meet each others’ eyes as the tentacles pressed them together and wiggled them suggestively, arranging them first against each other and then on either side of Mary.

“Why are you like this?” John demanded of Mary, though it was a rhetorical question really, and it was swallowed up in the kiss that the tentacles demanded, wet and heated and slippery, and enhanced by two little fingerlings that insinuated themselves into their pressed-together mouths, rippling and teasing and infusing them with the taste of a honeyed ambrosia.

“You’re drawn to high weirdness, John. Mysteries. Things that cannot and should not be. Freaks!” Sherlock said.

“But she wasn’t supposed to be like that! Why is she like that?”

“Because you chose - Urgh!” and now it was John and Mary’s turn to gaze upon the spectacle of Sherlock’s lush mouth stretched and plundered by a slick blue coil. Mary shivered in ecstasy as Sherlock met the challenge and, with narrow, calculating eyes, he licked and sucked it with unabashed gusto, nodding his head up and down its length slowly as though he’d had practice.

“That feels good?” John couldn’t help but asking Mary, because the tentacle gripping him between his thighs was starting to change the direction of his blood flow. And somewhere buried deep under the floorboards of his mind cottage were a few fleeting images that did seem to include glimpses of a body that could belong to no one but Sherlock playing a role in his and Mary’s marital relations. The idea of watching him pleasuring her did things for him, he had to admit. Even if tentacles hadn’t come into his incredibly brief and guilty bursts of menage-a-trois fantasy.

“Oh yes,” Mary said, panting and biting her lip. “It really, really does.”

“Oh God,” John said, reduced to meaningless blasphemies as the tentacles divined another hidden desire. Sherlock’s arms were now bound in quivering coils, and now one of those big, graceful hands of his was being guided right to John’s own danger zone - currently incited by the lewd tentacles to a level of arousal that was uncomfortable in his jeans. His jeans were being picked open by delicate fingers that mimicked human ones although they were not. Now his belt was open and his fly was down, and his hot, blood-hard cock was free and bare in the cool air only a moment before he was taken over and surrounded by a slender tentacle at the base, and Sherlock’s hand near the crown.

“My dear Watson,” Sherlock whispered. “A remarkable mutation of your own!”

“It’s all natural, Sherlock. Unlike hers,” John growled as those two different, distinctive types of grip began to stroke and tease him. He felt hot, tight, cradled, a little slick and wet - was that his own pre-come or the tentacles’ own lubrication, and heavenly hell, how had he come to find himself in a position to even ask himself such a question, and how did he suddenly care so little about the answer?

It wasn’t tentacles that pushed Sherlock and John’s faces together for a lewd, deep kiss - it was Mary’s hands as she laughed softly. “This was bound to happen one way or another, wasn’t it?”

Past the point of objecting, Sherlock and John made eye contact and agreed with a nod, leaning in to taste each other deeply, licking and nipping, a sliding clench and a tease of tongues. Mary moaned and licked her lips in sympathy as she watched, and her tentacles seemed to tighten around them both and bring them in against her.

Sherlock made a broken groaning sound into John’s mouth, and they all heard more fabric parting and tearing, a subtle shimmying of Sherlock’s body as the ruins of his trousers were pulled from his hips. John and Mary looked down to see his shapely dark pink cock arising from a dark thatch of hair - nothing heroic in size, but noticeably, if slightly, above average. Undeniably eager and ready to participate. John and Mary competed with each other in swiftness to take hold of it first, but Mary was of course very unfairly advantaged.

In retaliation, Sherlock had Mary’s brassiere off with unexpected speed and skill, in an instant one full breast cupped in his long-fingered hand, teasing her as he broke from John’s mouth and fixed his lips onto hers, but leaving room. Tentacles grasped and lifted bodies and positioned the three of them artfully, so there was little awkwardness as John’s tongue breached both Sherlock and Mary’s locked mouths, dancing and tangling; John finally managed to get a hand free to slide practiced fingers into Mary’s soaked knickers.

She whimpered and squirmed, desperate for more friction, and at last ripped off her own useless underpants with her own tentacle, before sliding its very tip around her own labia alongside John’s fingers. 

“Hey,” John said. “Don’t I know what you like?”

“Course you do, love,” she said, grinning. “But so do I.”

As she writhed and undulated shamelessly, caught between John’s hands between her thighs and Sherlock’s hands at her breasts - mouths at her neck, two of them, sometimes kissing and sucking, sometimes biting, sometimes leaving her to tease each other. 

Her tentacles moved almost independent of her own thought, often a few probings and thrustings well ahead of her. The tentacles seemed to learn very quickly where both Sherlock and John were sensitive, that John liked a rougher stroke on his cock and Sherlock loved his balls lightly tugged, and proved to both of them that their bodies were all in favor of having their thighs spread forcefully and their arseholes probed with tonguelike lappings and fingerlike thrustings. Though John initially put up a bit more of a resistance, it was he who shouted louder and came quicker, coating the inside of his cock-wrapping coils with copious cream. 

And Sherlock came hardest when Mary pressed his fingers against her and let him feel her orgasmic contractions and hear her cries in his ear. His teeth snapped at the air and his head fell back as he clenched his legs - both the one wrapped around Mary and the one wrapped around John - and impaled himself harder on the tentacle inside him and drove into the one wrapped tight around his cock, surrendering at last as one stray limb could not resist lightly squeezing his long bared neck.

The moments that came then were mostly full of heavy breathing, and gentle and careful recalibration. There could have been an awkward moment of avoided eye contact - well, to be fair, there was, but as they gradually came back to themselves, Mary and Sherlock and John realised they were holding hands in a circle, and there was no one who was not being touched by both of the others.

The moment was broken by everyone being dropped out of their cosy sort of rope nest as Mary’s tentacles untangled and suddenly withdrew - vanishing from whence they had come, that mysterious imperceptible storage pocket in her back.

All of them were more naked than not, sitting stewing in their own juices on the threadbare rug as Mary laughed. “They’re tucked in! They went back in! It’s so hard to get them do that!”

 

 

***  
“You understand now, don’t you?” Mary said as she let John guide her towards Sherlock’s bedroom, each of them with a hand pulling Sherlock with them. “The secrets I was so desperate to keep? Magnussen must have had a contact at Baskerville, I don’t know who or how, but it got out. If anyone knew the experiments on me were successful...if they could be replicated on others...and if they knew I was pregnant?”

“I understand a lot better, yeah,” John said in a shaky voice as he laid Mary down in Sherlock’s huge bed and laid a blanket over her and not even blinking as Sherlock crawled in beside her. “But we made progress, we already know more about how to control them, don’t we?”

“They need...satisfaction,” Mary said darkly, and Sherlock nodded on the pillow beside her as if he was completely unsurprised.

“They needed to kill,” Sherlock said quietly.

“At first. That was the only way to retract them that I was taught. Luckily, I later found that a good swim in salt water could satisfy them. But I had to be so careful not to be seen. But now, now that I know that another foolproof way to make them happy is just _bringing them out for hot sex?”_ Her tired eyes were shining, tears of joy and relief in her lashes. She curled up against Sherlock and drew John down into her arms. 

“Then some would still take you and do anything to expose your secret,” Sherlock said somberly. “Especially now that there is a potential...commercial benefit.”

“We’ll do anything to keep you safe, Mary,” John said.

“Thank you both so much, but…”

“Well, if that’s what takes, then it’s hardly a burden,” Sherlock said with a sideways grin.

**Author's Note:**

> This story now has a sequel! [Filled Afresh With Each Flow](https://archiveofourown.org/works/9871127). In which The Six Thatchers ends differently.


End file.
